Negatives of full Fibreglass hulls/decks?

[Cheechako]

[QUOTE=goboatingnow;3502984]

Originally Posted by BillKny

Solid grp in decks would be way too bendy and would require wooden boat style supports under it. Which is why it existed for a while as early builders didn’t understand if.

Cored is far more rigid

I think a case could be made for solid decks (they were made that way early in FG contruction) but were sometimes a bit flexy though. No strength issues, just not a "feel" people liked. With the myriad of wet cored decks out there, what would be nice would be solid decks with a lattice structure to stiffen it say in 6" squares... so effectively small ribs in a squarish pattern for the large flat surfaces. Near other buildups like cabin trunk or toe rail it needs nothing.
Too expensive I guess. But I have often wondered "what am I getting when paying a premium for a Swan?" For the money, things like this should be offered!

The other interesting thing, the boat in my avatar (Taiwan built) the deck glass was about 3/8" thick. It really needed little support at all although it had coring.

[Cheechako]

Originally Posted by Rucksta

I did some penetrative testing on solid and composite panels at the firing range.

Small holes in composite, large chunks out of solid.

Counter intuitive but my anecdotal observations over the years suggest cored boats fair quite well being dragged over the reef - salvage not grounding - and are easily repairable.

No input regards hitting containers, ice bergs or whales

It's really irrelevant for boat building unless you are building for the Navy (which I have) , otherwise we should make hulls out of Gel, as it resists gun shots better yet.

[redneckrob]

[QUOTE=Polar Opposite;3503554]

Originally Posted by redneckrob

I've owned two 30'+ boats with solid fiberglass decks...a Contest 32 ketch and a CSY 33 cutter. Both were/are rugged cruising boats. All CSYs were solid fiberglass decks, and defined the concept of "overbuilt". I'm not a marine architect, but I don't notice any more vertical support on the interior than any other production boat, and I don't notice any more condensation either. Nor did either deck ever noticeably 'flex". I would guess that the reasons to not do it are more driven by reducing construction costs, complexity and topside weight than by any other considerations.

I'm pretty sure they stopped making those when I was in grade school (I'm nearly 50 now!). I don't know of anyone building solid decks in larger boats in the modern era, i.e. in the last decade.

[Lucky Luke 1]

Originally Posted by Benz

I'm not sure there's a difference for lightning strikes, unless your ply is wet and thus conductive, which also means the boat is worthless, or soon will be.
Despite differing opinions, you'll notice that nobody here had advocated a ply-cored hull. That's because it's a bad idea. The closest to that you can safely get is a cold-molded timber-and-epoxy hull, which are quite strong and durable, if built right and maintained well (best sea boat I ever sailed was one of these).
But if you're asking which method of construction is better for lightning, perhaps you don't know yet what questions to ask.

Thanks for your reply. No im not asking which construction method is better defence against lightening i was asking I'm under the assumption that a full fibreglass hull is less likely to be holed in the advent of a lightning strike than glassed over ply or composite. True or false?

Reason i asked is i saw a mechanical engineer state this and id like peoples real world opinions or learned opinions.

[boatpoker]

Originally Posted by Lucky Luke 1

i was asking I'm under the assumption that a full fibreglass hull is less likely to be holed in the advent of a lightning strike than glassed over ply. True or false?

Reason i asked is i saw a mechanical engineer state this and id like peoples real world opinions or learned opinions.

Thousands of surveys under my belt and I've never heard of a glassed over ply production boat. Please identify which model you are asking about.

I've seen a few backyard junkers built that way but they don't last long.

[Copacabana]

Originally Posted by boatpoker

Thousands of surveys under my belt and I've never heard of a glassed over ply production boat. Please identify which model you are asking about.

I've seen a few backyard junkers built that way but they don't last long.

The only production builder in plywood and glass that comes to mind is RM in France.

https://www.rm-yachts.com/en/rm-yachts-know-how/#

https://www.rm-yachts.com/

There are a lot of home-built ply-glass boats in Brazil and they seem to be standing up pretty well. Dudley Dix also designs for Ply-glass construction.
Personally, I'd go with glass over rigid PVC foam or Divinicell, but ply seems to get the job done.

[Lucky Luke 1]

Originally Posted by boatpoker

Please tell me the make of a production boat with a glass over ply hull.

I should of used the word Composite instead of Ply. I'm guessing the big names these days use foam cell i know Kraken use CF added to the impact points and full tying off of the metal areas to limit lightening strikes damage. Not cheap boats though..
I had a Cruise Craft 15ft that was glass over ply it was a production boat from the early 80's.

[boatpoker]

Originally Posted by Copacabana

The only production builder in plywood and glass that comes to mind is RM in France.

https://www.rm-yachts.com/en/rm-yachts-know-how/#

https://www.rm-yachts.com/

There are a lot of home-built ply-glass boats in Brazil and they seem to be standing up pretty well. Dudley Dix also designs for Ply-glass construction.
Personally, I'd go with glass over rigid PVC foam or Divinicell, but ply seems to get the job done.

RM are cold molded, not what I would call "glass over ply".
I have no knowledge of how well "glass over ply" works in Brazil

[Lucky Luke 1]

Originally Posted by boatpoker

Thousands of surveys under my belt and I've never heard of a glassed over ply production boat. Please identify which model you are asking about.

I've seen a few backyard junkers built that way but they don't last long.

I should of used the word Composite.

Not asking about a particular model.

[Copacabana]

Originally Posted by boatpoker

RM are cold molded, not what I would call "glass over ply".
I have no knowledge of how well "glass over ply" works in Brazil

No, RM use plywood. From their site:

"All our RM1070+ are mostly made of plywood-epoxy"

and

"RM Yachts are “composite”, as much as the best materials are carefully selected for each part of the boat.

Plywood for the general structure – Epoxy stratification for the assembly – Iron for the keel – Polyester sandwich for the roof – And from now on epoxy sandwich for the planking above waterline (1180)."

Nothing wrong with the material if used properly. RM are pretty high-end boats BTW.

[boatpoker]

Originally Posted by Copacabana

No, RM use plywood. From their site:

"All our RM1070+ are mostly made of plywood-epoxy"

and

"RM Yachts are “composite”, as much as the best materials are carefully selected for each part of the boat.

Plywood for the general structure – Epoxy stratification for the assembly – Iron for the keel – Polyester sandwich for the roof – And from now on epoxy sandwich for the planking above waterline (1180)."

Nothing wrong with the material if used properly. RM are pretty high-end boats BTW.

Their website describes cold molding and yes cold molding involves plywood but is nothing like "glass over ply".

[Copacabana]

Originally Posted by boatpoker

Their website describes cold molding and yes cold molding involves plywood but is nothing like "glass over ply".

Can you point me to that part on their site? It seems to me they use plywood for the structure of the boat (they are not laminating thin layers of wood in epoxy to "mold" the hull as far as I can tell). You can really see the ply panels in the hull shape (chines). Perhaps I misunderstood the concept of cold molding.

[Copacabana]

Originally Posted by boatpoker

Their website describes cold molding and yes cold molding involves plywood but is nothing like "glass over ply".

https://www.youtube.com/watch?v=M8weNSDvJJQ

https://www.youtube.com/watch?v=9N2UeWmXOzY

[Jim Cate]

No comment about the quality of the RM line of yachts, but they say:

"
"RM Yachts are “composite”, as much as the best materials are carefully selected for each part of the boat."

Followed by stating that iron is used in the keel. IMO (and that of most designers) is that lead is a better ballast than iron. Leads one to question their other selections.

They do have a good reputation in the community, so my nit-picking is likely not relevant, and the ability of any non-conductive hull material to withstand a direct lightning strike is questionable. For safety in a strike, I believe that a metal hull is the only useful alternative.

Jim

[Nicholson58]

All glass boats are desired by many. Infinitely repairable. The only negative is they are not suitable foe high latitudes. As long as you stay in swimsuit territory, who cares.